1) Preheat the oven to 350 degrees.
2) Season the beef brisket with salt, and place in a baking dish.
3) Cover the entire roast with the onion slices.
4) Mix together the beer, brown sugar, beef bouillon, pepper, garlic, bay leaf and thyme.
5) Pour beer mixture over the roast and cover with aluminum foil.
6) Bake for 4 hours.
7) Mix together the cornstarch and water.
8) Remove brisket from baking dish and stir cornstarch mixture into the juices.
9) Cook over medium heat until thickened.
10) Slice meat and serve with sauce.